Synthesis of Titanium Dioxide in Hydrogen Peroxide Solution and Its Photocatalytic Character

TiO2 nanocrystals were synthesized from Titanium Tetraisopropoxide in H2O2 solution, and utilized as photocatalysts for degradation of humic acid in aqueous solution. The highly pure TiO2 nanocrystals were obtained by excluding the use of inorganic acids that might consequently cause contamination of active catalytic surface sites of the nanocrystals by Cl-, NO3- and SO42-. Particle size and crystallinity of the nanocrystals were increased with progressing the refluxing time 1 similar to 9 h at 120 degrees C in an oil bath. By varying H2O2/Ti = 5.5 similar to 55, the crystalline phase of anatase/rutile ratio of the nanocrystals was controllable. The photocatalytic properties of the nanocrystals were strongly dependent upon the crystallinity and particle size. The DOC removal of humic acid was most effective for the nanocrystals prepared at H2O2/Ti=5.5 due to the mixed crystalline phase of anatase/rutile and the increased surface area by smaller particle size. The decreases of UV254 absorbance of HAs solutions were much faster than those of DOC, and not so dependent upon the variations of TiO2 nanocrystals.